1. Field of the Invention
The present invention relates generally to pipe fittings and, more particularly, to a tee provided at the inlet and/or outlet of a septic tank and other on-site waste disposal systems. The tee can be used as a housing for an effluent filter at the outlet of a septic tank, and can also be used without an effluent filter, in place of conventional pipe tees at the inlet of a septic tank.
2. Background
Most septic systems and other on-site waste disposal systems utilize pipe couplings, known in the art as so-called tees, for directing and controlling flow of sewage into, or effluent out of, the tank of the disposal system. Older concrete septic systems utilized cast-in concrete baffles at the inlet and outlet of the system. A drawback of concrete baffles is that the exposed portion thereof, i.e. that portion of the concrete baffles which is above the level of the scum layer within the septic tank, rapidly deteriorates. This is understood to be a result of exposure to gases within the tank. A recent trend to overcome this drawback has been the use of plastic tees to replace concrete baffles at both the inlet and outlet of the septic tank. Such a tee, also called a tee baffle, is often provided at the outlet of the disposal system to serve as a housing for an effluent filter, whether as a so-called multi-pass filter, as described in co-pending U.S. patent application Ser. No. 09/338,371, or as a so-called single-pass filter, as typified by U.S. Pat. No. 5,382,357. Alternatively, such a tee can be used at the inlet end of the disposal system, without a filter, so as to direct sewage to the bottom of the septic tank or other on-site waste collection tank. The tee baffle can have a right-angle shape, or more preferably, be in the form of a sanitary tee-type baffle, in which case it has an arching, or “sweep” design portion at the inlet/outlet port.
Typically, installers of septic tanks and other on-site waste disposal systems use standard tees or sweep tees manufactured primarily for use in plumbing applications, such as for pipe joints or couplings. As a result, such standard tees and sweep tees are not universally adequate for serving as the housing for an effluent filter inside the septic tank. They are relatively heavy, and relatively expensive for use in septic systems.
Another drawback of conventional tees is the difficulty and expense of molding such tees. Due to the necessity of having three openings and a hollow interior, complex molds are necessary to achieve a molded one-piece tee. Most injection molding techniques presently used to manufacture pipe tees leave undesirable interior seams and flash, which tend to impede insertion of effluent filters into the pipe tees, and adversely effect operation and sealing of the effluent filters and pipe tees. Also, because grease, fats, oils, hair, lint, and other floatables in effluent tend to collect at rough surfaces along the interior wall of a conventional pipe tee to thereby cause flow blockage, such seams or flash provide surfaces where such undesired waste products are likely to be deposited. Over time, solid and semi-solid waste in the effluent will build up, and slime will grow at such seams or flash, the combination eventually prematurely plugging the pipe tee. This undesirable plugging also detrimentally effects the needed sealing surfaces for the annular seals used with many prior art single-pass filters.
A recognized problem with conventional pipe tees used in on-site waste systems is that, once they start to become plugged, it is more difficult for the effluent to make its way through the pipe tee, through an effluent filter held therein, and out the outlet of the septic tank. Eventually, due to such plugging, among other reasons, the effluent in the septic tank rises to a level higher than the level of effluent in the pipe tee. This fluid level differential causes a build up of pressure, or head pressure, that is exerted on and within the open base of the pipe tee, i.e. in the region of the bottom of the effluent filter. In many cases, these head pressures undesirably cause the effluent filters to literally pop up out of the pipe tees. It would therefore be desirable for an effluent filter housing to not only help prevent premature plugging, but also include means for preventing the effluent filter from undesirably popping out of the tee housing.
Since conventional pipe tees are formed as relatively short-length plumbing couplings, they are not of sufficient length to encase or house any of the currently available effluent filters. Most known commercial single-pass effluent filters, as well as the multi-pass effluent filter that is the subject of co-owned U.S. patent application Ser. No. 09/338,371, require a generally cylindrical housing extending to cover much, if not all, of the extended length of the effluent filter. This is required in order to provide regions for filtered effluent to eventually reach the outlet port of the tee, and thereby exit the tank portion of the system, all without again mixing with unfiltered sewage.
Such generally cylindrical filter housings are usually provided by way of a length of PVC pipe cut down to fit one end of the available plumbing tees, and of sufficient length to cover the sealing gasket used with many of the known single-pass effluent filters. The gasket provides a sealing membrane between the effluent filter and the inner wall of the length of pipe, to substantially isolate a region therebetween to receive filtered effluent. Because commercially available PVC pipe is widely sold in lengths on the order of no shorter than 10′, it is not uncommon for the installer to cut off a relatively short length of pipe, e.g. 12″, from a 10′ pipe section for coupling with a standard plumbing tee to thus create the needed cylindrical housing for the effluent filter.
It is also recognized that health-related codes and regulations in some jurisdictions, i.e. municipalities, counties, and states, require the elongated portion of pipe tees used in septic tanks to extend lower, i.e. deeper into the clear zone of the effluent in the septic tank, than is minimally necessary for the elongated portion of the tee to cover the effluent filter. It would be desirable, for use in such jurisdictions, and in other instances where longer tees are considered beneficial, such as for use in relatively deeper septic tanks, to easily adapt a pipe tee by lengthening the elongated portion thereof. In conventional tees, one would likely cut the length of pipe to its final desired length before connecting the pipe to the pipe tee. For example, when so-called schedule 40 pipe is used for extending a schedule 40 tee used in a septic tank to house an effluent filter; the schedule 40 pipe has a wall thickness of about 0.250″. An extendable pipe tee that had a reduced wall thickness would therefore reduce the material needed for the effluent filter housing, yet still could be adaptable for use where longer pipe tees were desired.
One reason that such thick-walled pipe is used in conventional plumbing pipe tees is that such pipe must satisfy pressure-rated fitting requirements for use in non-septic tank locations, non-drainage locations, and under-floor locations, as well as in other applications where the pipe tees are subjected to high external pressures. Furthermore, those thick-walled pipes may be subjected to, and are made to withstand, high internal pressures, which are simply not encountered in septic tank and similar drainage systems. Because pipe tees used solely at the inlets and outlets of septic tanks and other on-site waste drainage systems are not used in under-floor applications, they are also not subjected to the high external pressures that typical plumbing tees must withstand. Thus, in septic tanks and other on-site drainage systems, pipe tees (whether installed at the inlet or outlet end) could be made in a way that substantially saves on molding materials and manufacturing costs, while still meeting, and even exceeding, the much lower internal and external pressure demands the pipe tees would encounter.
It would be desirable for pipe tees used in septic tanks and other on-site waste drainage systems to be made substantially thinner-walled than conventional pipe tees, yet still maintain sufficient structural integrity to withstand some forces, such as internal forces exerted during insertion or removal of effluent filters into or from the pipe tee. It would further be desirable for such a thinner-walled pipe tee to have a spigot or pipe-size end at the lowermost end thereof that has an outside dimension that is compatible with the inside of the bell end of an SDR 35 pipe or the hub of a sewer and drain SDR-35 fitting, so that in septic tanks, the pipe tee could still be connected to a bell end of a thin-walled pipe, as well as to the hub of an SDR-35 fitting (also known in the art as a sewer and drain fitting), ASTM 3034, ASTM 2729 pipe or bell. It is preferable to still use such thicker walled pipe as connections to the inlet and outlet ends of a septic system, but the present invention is directed toward avoiding the expense of such thicker walled tubing for the tee baffle on the interior of the septic tank, where such internal and external pressures are not encountered.
It is an object of the present invention to provide a tee suitable for use at the inlet or outlet of a septic tank or other on-site waste system that is relatively inexpensive.
It is another object of the present invention to provide a tee baffle with its own integral generally cylindrical portion that can provide a housing for many of the commonly available effluent filters having generally cylindrical profiles. Even at the outlets of septic tanks located in jurisdictions where effluent filters are not presently required or commonly used, it would still be desirable to use such tee baffles, because it may eventually become desirable to add an effluent filter at a later date, to meet later code requirements. The tee baffle of the present invention should therefore provide a way to later easily add an effluent filter at the outlet without having to then retrofit the septic tank with a special housing for the effluent filter.
It is a further object to provide specific structure for a tee baffle that promotes efficient operation of a given known effluent filter, whether of the single-pass or multi-pass type, yet does not interfere with the successful use of the tee with other known circular-shaped effluent filters. The manner in which these and other objects of the invention are achieved will become clear in the following Summary of the Invention, the drawing figures, and the Detailed Description of the Preferred Embodiment.